季节冻土区盐渍土环境下混凝土抗冻耐久性机理

为了研究混凝土在冻融交替与盐类侵蚀双重因素作用下的抗冻耐久性能,根据季节冻土区大安境内盐渍土中主要易溶盐的类型与含量,配制了3种质量分数的复合盐侵蚀溶液,制备了普通混凝土、2种引气混凝土及2组粉煤灰混凝土试件,进行盐蚀[CD*2]快速冻融循环试验,对盐冻破坏后混凝土的质量损失、动弹性模量衰减及其微观结构进行分析。试验结果表明:在冻融循环作用下,复合盐加剧了混凝土的冻融剥蚀破坏;混凝土的冻害程度与侵蚀盐溶液的质量分数、冻融循环次数、混凝土的含气量、粉煤灰掺量等因素有关;造成混凝土发生盐冻破坏的原因有水结成冰的膨胀压力,或冰与水的渗透压力以及复合盐与水泥水化产物发生的化学侵蚀和盐类的结晶膨胀,其中,盐类结晶压对混凝土内部结构的破坏更严重。     

复合盐与干湿循环双重因素作用下混凝土耐久性试验

吉林省大安市是松嫩平原土壤盐渍化最严重的地区之一,以苏打盐渍土为主,境内的土壤与地表水中的易溶盐分量相似。为了研究复合盐与干湿交替环境下混凝土的耐久性,根据大安地区盐渍土中主要易溶盐的含量,配制了4种不同质量分数的复合盐侵蚀溶液,再以水溶液用于试验对比,共制备了5种配合比的混凝土,进行盐浸-热烘试验。结果表明：在干湿循环条件下,复合盐对混凝土材料有较强的腐蚀性,而且盐溶液的质量分数越大,混凝土破坏越严重;干湿循环作用后,混凝土的质量变化规律为先增加后减少,而动弹性模量先呈小幅增长,达到一定干湿循环次数后,呈下降趋势;引气剂与粉煤灰均能够提高混凝土抗盐蚀-干湿循环的破坏能力,但引气混凝土提高效果更显著。     

基于应力腐蚀和腐蚀疲劳的焊缝磁记忆信号分析

为了研究不同腐蚀条件下的焊缝磁记忆特征信号,对20号钢板状焊缝试件进行残余应力腐蚀、35kN恒拉伸应力腐蚀和35kN静载、25kN动载拉拉腐蚀疲劳对比实验,分析焊缝正、反面磁记忆信号的变化规律,获得焊缝腐蚀发展进程中应力腐蚀与腐蚀疲劳各自对应的磁记忆特征信号.结果表明:在应力腐蚀状态下,不同拉伸载荷对应的磁记忆信号特征不同,35kN恒拉伸应力腐蚀与残余应力腐蚀相比,焊缝区磁记忆信号峰峰值及其梯度更大,磁记忆曲线分布的分散度更大;35kN静载、25kN动载拉拉腐蚀疲劳与35kN恒拉伸应力腐蚀相比,焊缝区磁记忆曲线上下波动多,过零点次数多,磁记忆曲线分布的分散度小.这为磁记忆技术在焊缝工程检测的定性与定量分析提供基础数据.     

城市热岛效应下浅层土中混凝土的酸腐蚀试验研究

针对城市热岛效应引起城区浅层土地温场升高这一观测结果,采用室内快速模拟试验方法,对城区酸性土壤腐蚀混凝土材料的温度效应开展了试验研究。试验研究了在温度为5℃、20℃和40℃条件下,混凝土试样在酸浓度分别为0%、5%和10%的沙土介质中放置30d、90d后的抗压强度变化规律,并对混凝土试样在腐蚀过程中的腐蚀系数变化规律和微观机理进行了分析;最后,对南京城区热岛效应环境下浅层土中混凝土材料酸腐蚀的强度变化规律进行了分析。试验结果表明,在同一腐蚀浓度下,混凝土试样抗压强度的下降速度随着温度的升高而不断加快,其腐蚀系数也随着温度的升高而不断增大;腐蚀介质的浓度越大,环境温度对混凝土腐蚀系数的影响就越明显;在温度为40℃、硫酸浓度为10%的沙土中放置30 d后,混凝土的腐蚀系数K达到45.21%,约是在5℃条件下腐蚀系数的2倍,相当于环境温度每上升1℃,混凝土腐蚀系数平均增加0.64%。该研究成果对于减轻城市热岛效应对岩土工程的影响具有重要意义。     

珠江口盆地流花碳酸盐台地灰岩坑的地震反射特征及成因探讨

早中新世东沙隆起带上发育了大规模的流花碳酸盐台地,上覆巨厚未固结-弱固结泥岩。基于三维地震数据,利用相干体及可视化等方法,在台地上发现了由溶蚀垮塌作用形成的数量众多的椭圆形的灰岩坑。灰岩坑直径一般为200~700 m,最大超过900 m,深度10~90 m;灰岩坑在地震反射上表现为碳酸盐岩顶部垮塌,并导致上覆泥岩地层塌陷;灰岩坑一般沿NWW向断层分布,这些NWW向断层切割中新世碳酸盐岩和上覆海相泥岩地层,绝大多数终止于T₁₀的不整合面。综合分析东沙海区构造和沉积过程认为：发生在晚中新世末期的东沙运动形成了NWW向张扭性断层,为酸性流体提供了运移通道和物质交换场所;东沙运动伴生的基底岩浆活动可能产生了酸性热液流体;东沙运动末期发生强烈的构造抬升和大规模海底暴露,造成地表水沿断层注入,加快了碳酸盐岩的溶蚀速率。在台地底部珠海组砂岩层的高压流体、地表水和岩浆活动可能产生的酸性热液流体的共同溶蚀作用下,碳酸盐岩地层内部产生溶洞,并且越来越大,最终顶部无法承载上覆巨厚泥岩而发生垮塌,形成灰岩坑。流花碳酸盐台地灰岩坑的形成不是简单的暴露溶蚀,而是构造活动影响下深埋藏溶蚀作用的产物。     

岩土预应力锚固结构服役寿命研究

岩土预应力锚固技术在交通、水利和建筑工程中得到了广泛应用,但工程实践表明,预应力索（杆）体由于使用环境和条件的特殊性,如长期埋置于潮湿的环境中和承受张拉作用力,存在着失效破坏现象。在相关研究的基础上,通过对比分析影响预应力锚固结构服役寿命的主要因素,确定杆体材料应力腐蚀是决定正常使用条件下预应力锚固结构服役寿命的根本因素。在利用流变力学理论和实际监测数据建立预应力长期变化模型、依据室内快速腐蚀试验和现场腐蚀监测数据建立杆体材料应力腐蚀发展模型基础上,以杆体材料变化的极限承载能力为判据,提出岩土预应力锚固结构服役寿命预测方法,可为岩土预应力锚固结构失效风险预防和处置提供指导作用。将研究成果应用于工程实践,预测了实际工程的服役寿命。     

元坝长兴组超深层生物礁大气田优质储层发育机理

通过系统开展元坝气田长兴组超深层生物礁储层岩石学与岩石地球化学分析,结合碳酸盐岩溶蚀动力学模拟实验,以及储层古压力恢复,揭示了元坝超深层生物礁优质储层的发育保存机理。研究表明,早期暴露溶蚀、浅埋藏白云岩化是基质孔隙发育的基础,储层深埋引起的古油藏原油裂解导致的超压水力破裂缝的形成,是储层渗透性改善的关键,"孔-缝耦合"共同控制了超深层优质储层的发育。在此基础上,构建了生物礁非均质"孔-缝双元结构"储层模型,为生物礁储层预测奠定了理论基础。     

Corrosion behavior of anodic oxidized TiO<Subscript>2</Subscript> film in seawater

TiO₂ films were formed on metallic titanium substrates by the anodic oxidation method in H₂SO₄ solution under the 80V D.C.. Phase component and microstructure were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Water contact angles on titanium oxide film surface were measured under both dark and sunlight illumination conditions. Corrosion tests were carried out in seawater under different illumination conditions by electrochemistry impedance spectrum (EIS) and polarization curves. The result showed that the TiO₂ film prepared by the anodic oxidation method was anatase with a uniform structure and without obvious pores or cracks on its surface. The average water contact angle of the film was 116.4° in dark, in contrast to an angle of 42.7° under the UV illumination for 2 hours, which demonstrates good hydrophobic property. The anti-corrosion behavior of the TiO₂ film was declining with the extended immersion time. Under dark conditions, however, the hydrophobic TiO₂ film retarded the water infiltrating into the substrate. The impedance changed slowly and the corrosion current density was 2 orders of magnitude lower than that with the film illuminated by sunlight. All of those mentioned above indicate that the TiO₂ film possesses much better performance under dark condition, and it can be applied as an engineering material under dark seawater environment.     

Mechanical and low-cycle fatigue behavior of stainless reinforcing steel for earthquake engineering applications

Use of stainless reinforcing steel (SRS) in reinforced concrete (RC) structures is a promising solution to corrosion issues. However, for SRS to be used in seismic applications, several mechanical properties need to be investigated. These include specified and actual yield strengths, tensile strengths, uniform elongations and low-cycle fatigue behavior. Three types of SRSs (Talley S24100, Talley 316LN and Talley 2205) were tested and the results are reported in this paper. They were compared with the properties of A706 carbon reinforcing steel (RS), which is typical for seismic applications, and MMFX II, which is a high strength, corrosion resistant RS. Low-cycle fatigue tests of the RS coupons were conducted under strain control with constant amplitude to obtain strain life models of the steels. Test results show that the SRSs have slightly lower moduli of elasticity, higher uniform elongations before necking, and better low-cycle fatigue performance than A706 and MMFX II. All five types of RSs tested satisfy the requirements of the ACI 318 code on the lower limit of the tensile to yield strength ratio. Except Talley 2205, the other four types of RSs investigated meet the ACI 318 requirement that the actual yield strength does not exceed the specified yield strength by more than 18 ksi (124 MPa). Among the three types of SRSs tested, Talley S24100 possesses the highest uniform elongation before necking, and the best low-cycle fatigue performance.     

中国南海涠洲油田W114A平台服役15年的水下钢结构腐蚀防护调查

介绍了W114A平台在南海服役15年的水下钢结构的腐蚀与防护特检报告.检测表明,生物污损严重,最大附着厚度可达20 cm,阴极保护系统正常,保护效果良好.对检测方法和结果进行了分析发现,电位测量程序不妥,牺牲阳极物理尺寸的测量方法不准确,测厚点的基面清理不干净,不能准确地对平台的阴极防护效果进行评估,并对此提出了修改意...